The protected lanes are designed to improve safety for cyclists by creating a physical barrier — a parking lane or flexible posts — between moving vehicles and bikes.

But in many of the selected locations, sections of the roadways fall under state jurisdiction. The Illinois Department of Transportation won't allow protected bicycle lanes to go on state-designated routes until it is satisfied they are safe, officials said.

IDOT will collect at least three years' worth of traffic accident data and then make a determination based on the analysis, officials said, adding that the existing information is inadequate because protected bike lanes are new here.

"We don't want to make decisions on a scattershot basis. Our traffic engineers want to see more data on the impact of protected bike lanes,'' IDOT spokesman Mike Claffey said.

Claffey said IDOT has safety concerns that include the visibility of cyclists at intersections and operational issues like maintenance and snow-removal around protected bike lanes. Approving protected bike lanes for Chicago would open the floodgates to allowing all other local governments in the state to do the same, he said.

IDOT's go-slow approach may win applause from some drivers who think Chicago is going overboard, especially on such thoroughfares as Dearborn Street downtown, where critics say a new configuration with two-way protected bike lanes makes traffic nearly immovable and dangerous for pedestrians.

But some transportation professionals say IDOT should let Chicago move forward with its plan.

"With about 60 traffic crashes every day in Chicago that result in injuries and fatalities, why would IDOT put the brakes on a proven traffic safety strategy?" said Ron Burke, executive director of the Active Transportation Alliance, which promotes greater use of alternative transportation.

"Chicagoans want safer streets, and studies show that protected bike lanes create more order on the streets and reduce injuries involving bikes, pedestrians and cars," Burke said.

Steven Vance, a transportation planner who is a bicycling advocate, said IDOT's action is unwarranted because there is ample evidence from cities worldwide pointing to the safety benefits of protected bike lanes in reducing crashes.

New York City's protected bike lane on 9th Avenue led to a 56 percent reduction in injuries to all street users, including a 29 percent reduction in injuries to people walking, according to the city's transportation department.

"IDOT is being a little stubborn,'' said Vance, 28, who is deputy editor of Streetsblog Chicago, which covers sustainable transportation issues. He was first to blog about IDOT's policy imposing a "moratorium'' on the city's installation of protected bike lanes.

"IDOT says the safety performance of protected bike lanes is inconclusive, but there is a lot of information showing that the farther you can get a cyclist away from cars, the safer that cyclist will be,'' Vance said in an interview.

"I am concerned that IDOT will continue to find the data inconclusive. It seems IDOT doesn't want to be 100 percent pro-car (any longer), but they are having a difficult time making the transition.''

Claffey disagreed. IDOT revised its policies under the state's Complete Streets program approved by the General Assembly and signed into law by Gov. Pat Quinn three years ago, he said. As an example, he said, IDOT now pays 80 percent of the cost for localities to construct new bike lanes during road projects, compared with no state match previously.

Chicago's first protected bike lane was completed in July 2011 on a half-mile stretch of Kinzie Street between Milwaukee Avenue and Wells Street, so IDOT will continue to collect crash reports through at least half of 2014, officials said.

For the short term, it means there will be a patchwork of bike-vehicle separations on the streets that, some argue, could lead to confusion among cyclists and motorists and possibly cause or contribute to accidents.

On Jackson, the barrier-protected bike lane starts at Western Avenue, but it switches at Ogden Avenue to a buffered bike lane. The reason for the change is that Jackson is a state route between Ogden and Lake Shore Drive.

A buffered bike lane uses pavement markings to create more spacing than a typical bike lane provides between motorized traffic and bikes, but the buffered space lacks a physical barrier to protect cyclists from vehicles.